Tex. Education Code § 54.056

(a) If an institution of higher education erroneously classifies a person as a resident of this state and the person is not entitled or permitted to pay resident tuition under this subchapter, the institution of higher education shall charge nonresident tuition to the person beginning with the first academic term that begins after the date the institution discovers the error. Not earlier than the first day of that term, regardless of whether the person is still enrolled at the institution, the institution may request the person to pay the difference between resident and nonresident tuition for an earlier term as permitted by Section 54.057. For nonpayment of the amount owed, the institution may impose sanctions only as provided by that section. The institution may not require payment as a condition for any subsequent enrollment by the person in the institution.

(b) Regardless of the reason for the error, if an institution of higher education erroneously classifies a person as a nonresident of this state, the institution shall charge resident tuition to the person beginning with the academic term in which the institution discovers the error. The institution immediately shall refund to the person the amount of tuition the person paid in excess of resident tuition.